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BUG: KASAN: use-after-free in string_nocheck lib/vsprintf.c:641 [inline]
BUG: KASAN: use-after-free in string+0x21f/0x2b0 lib/vsprintf.c:723
Read of size 1 at addr ffff88811be8d0b9 by task syz.9.3103/12082

CPU: 1 PID: 12082 Comm: syz.9.3103 Tainted: G        W         syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/14/2025
Call Trace:
 __dump_stack+0x21/0x24 lib/dump_stack.c:77
 dump_stack_lvl+0x169/0x1d8 lib/dump_stack.c:118
 print_address_description+0x7f/0x2c0 mm/kasan/report.c:248
 __kasan_report mm/kasan/report.c:435 [inline]
 kasan_report+0xe2/0x130 mm/kasan/report.c:452
 __asan_report_load1_noabort+0x14/0x20 mm/kasan/report_generic.c:306
 string_nocheck lib/vsprintf.c:641 [inline]
 string+0x21f/0x2b0 lib/vsprintf.c:723
 vsnprintf+0xf20/0x1960 lib/vsprintf.c:2689
 seq_vprintf fs/seq_file.c:398 [inline]
 seq_printf+0x175/0x260 fs/seq_file.c:413
 input_devices_seq_show+0x1a6/0x650 drivers/input/input.c:1186
 seq_read_iter+0x93f/0xd30 fs/seq_file.c:272
 seq_read+0x3cc/0x4d0 fs/seq_file.c:162
 pde_read fs/proc/inode.c:321 [inline]
 proc_reg_read+0x1c4/0x2b0 fs/proc/inode.c:333
 vfs_read+0x1fe/0xa10 fs/read_write.c:494
 ksys_read+0x140/0x240 fs/read_write.c:634
 __do_sys_read fs/read_write.c:644 [inline]
 __se_sys_read fs/read_write.c:642 [inline]
 __x64_sys_read+0x7b/0x90 fs/read_write.c:642
 do_syscall_64+0x31/0x40 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x61/0xcb
RIP: 0033:0x7f7a27ba2ba9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f7a265ea038 EFLAGS: 00000246 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007f7a27dea090 RCX: 00007f7a27ba2ba9
RDX: 0000000000002020 RSI: 0000200000000040 RDI: 0000000000000007
RBP: 00007f7a27c25e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f7a27dea128 R14: 00007f7a27dea090 R15: 00007ffff86485c8

Allocated by task 0:
(stack is not available)

The buggy address belongs to the object at ffff88811be8d000
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 185 bytes inside of
 512-byte region [ffff88811be8d000, ffff88811be8d200)
The buggy address belongs to the page:
page:ffffea00046fa300 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88811be8c800 pfn:0x11be8c
head:ffffea00046fa300 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x4000000000010200(slab|head)
raw: 4000000000010200 ffffea0004399508 ffffea00047d3608 ffff888100043080
raw: ffff88811be8c800 0000000000100001 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 133, ts 5597418574, free_ts 0
 set_page_owner include/linux/page_owner.h:35 [inline]
 post_alloc_hook mm/page_alloc.c:2456 [inline]
 prep_new_page+0x179/0x180 mm/page_alloc.c:2462
 get_page_from_freelist+0x2235/0x23d0 mm/page_alloc.c:4254
 __alloc_pages_nodemask+0x268/0x5f0 mm/page_alloc.c:5370
 alloc_slab_page mm/slub.c:-1 [inline]
 allocate_slab mm/slub.c:1813 [inline]
 new_slab+0x84/0x3f0 mm/slub.c:1874
 new_slab_objects mm/slub.c:2632 [inline]
 ___slab_alloc+0x2a6/0x450 mm/slub.c:2796
 __slab_alloc+0x63/0xa0 mm/slub.c:2836
 slab_alloc_node mm/slub.c:2918 [inline]
 slab_alloc mm/slub.c:2960 [inline]
 __kmalloc_track_caller+0x1ef/0x320 mm/slub.c:4541
 __kmalloc_reserve net/core/skbuff.c:144 [inline]
 __alloc_skb+0xdc/0x520 net/core/skbuff.c:212
 alloc_skb include/linux/skbuff.h:1126 [inline]
 alloc_skb_with_frags+0xa2/0x560 net/core/skbuff.c:5993
 sock_alloc_send_pskb+0x853/0x980 net/core/sock.c:2388
 unix_dgram_sendmsg+0x5f4/0x17d0 net/unix/af_unix.c:1725
 unix_seqpacket_sendmsg+0x118/0x1e0 net/unix/af_unix.c:2108
 sock_sendmsg_nosec net/socket.c:652 [inline]
 __sock_sendmsg net/socket.c:664 [inline]
 sock_write_iter+0x29c/0x380 net/socket.c:1018
 call_write_iter include/linux/fs.h:2066 [inline]
 new_sync_write fs/read_write.c:518 [inline]
 vfs_write+0x725/0xd60 fs/read_write.c:605
 ksys_write+0x140/0x240 fs/read_write.c:658
 __do_sys_write fs/read_write.c:670 [inline]
 __se_sys_write fs/read_write.c:667 [inline]
 __x64_sys_write+0x7b/0x90 fs/read_write.c:667
page_owner free stack trace missing

Memory state around the buggy address:
 ffff88811be8cf80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88811be8d000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88811be8d080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                        ^
 ffff88811be8d100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88811be8d180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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